The present invention relates generally to pressurized fluid systems and more particularly, but not by way of limitation, to a pressure relief system which uses a trigger assembly with a collapsible member to establish a bypass or shutdown path for a pressurized fluid in response to an overpressure condition.
Pressurized fluid systems are typically provided with pressure relief capabilities to prevent the possibility of injury to humans and damage to equipment in the event of an overpressure condition. Such pressure relief systems often use a pressure responsive member that mechanically fails when subjected to a large increase in fluid pressure above a desired setpoint.
A particularly advantageous pressure relief system uses a buckling pin arrangement such as taught by U.S. Pat. No. 4,724,857 issued to Taylor. In such a system, the pin is placed under compressive load along an axial length of the pin by the pressure of the fluid. A sufficient increase in fluid pressure above a nominal operational level causes the pin to buckle, or collapse, allowing a plunger or other mechanism to move to a position where an overpressure path can be established to direct the fluid to reduce the pressure to a safe operational level. Such overpressure path can be established, for example, by opening a bypass valve or closing a shutoff valve.
While operable, it is desirable to isolate the operation of the buckling pin or other pressure responsive member from system forces associated with establishing the overpressure path for the fluid. For example, friction forces and fluid pressure can tend to offset the compressive load upon a buckling pin if the pin actuation and the valve are directly coupled. This can result in undesirably raising the set point at which the pressure responsive member begins to fail.
There is therefore a continued need for improvements in the art to increase the accuracy and repeatability of pressure relief systems, and it is to such improvements that the present invention is directed.
A pressure relief system is provided to detect and abate an overpressure condition in a pressurized fluid. In accordance with preferred embodiments, the system includes a housing having a housing interior surface which defines a housing interior chamber. The housing interior chamber extends along a selected axis.
An actuator assembly is coupled to the housing and is configured to establish an overpressure path for the pressurized fluid when a pressure of the pressurized fluid reaches a predetermined level. The actuator assembly comprises an extension sleeve which extends into and along the housing interior chamber, the extension sleeve having an extension sleeve outer surface in close proximity to the housing interior surface. The extension sleeve further has an extension sleeve interior surface which defines an extension sleeve interior chamber, said extension sleeve interior chamber extending along the selected axis.
A pressure response assembly is also coupled to the housing and comprises a pressure responsive member (such as a buckling pin) configured to mechanically fail in response to application of a compressive force established when the pressurized fluid reaches the predetermined level. The pressure response assembly further comprises a trigger member coupled to the pressure responsive member, the trigger member extending into and along the extension sleeve interior chamber. The trigger member comprises a first stem portion having a first stem outer surface in close proximity to the extension sleeve interior surface.
A number of retention members (preferably ball bearings) are provided adjacent the first stem portion of the trigger member. Each retention member extends through an aperture in the extension sleeve and into a recessed cavity formed in the housing interior surface.
The retention members prevent axial movement of the extension sleeve along the selected axis while the first stem portion remains adjacent the retention member. Upon mechanical failure of the pressure responsive member, the first stem portion is advanced along the selected axis past the retention member to allow the extension sleeve to advance the retention member out of the recessed cavity and along the housing interior chamber as the extension sleeve moves along the selected axis. The overpressure path for the pressurized fluid is established by the actuator assembly as the extension sleeve moves along the selected axis.
In this way, the trigger member, the extension sleeve and the retention members cooperate to function similarly to a xe2x80x9cquick-disconnectxe2x80x9d coupler, and system forces associated with the actuator assembly do not undesirably affect the set point at which the pressure responsive member begins to mechanically fail.